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Kinds of Selection, evolution evidence Natural Selection Both Lamark and Darwin stated that species change over time Lamark hypothesized that environment causes the changes in the organism Darwin hypothesized that environment chooses favourable variations, and that variation exists because of the different genetic composition of the population Aritificial Selection Using the principles of natural selection to domesticate wild organisms Chosing desirable characteristics and selectively breeding organisms Ex: dog varieties for hunting, racing, herding etc. Ex: plants selected for pest resitance, productivity etc. Accidental Selection Humans create unintentional changes in the genetic characteristics of organisms Ex: DDT resistant insects Ex: antibiotic resistant bacteria Evidence that organisms evolve over time Direct Evidence: Fossils Provide evidence for how organisms have changed Many fossils represent species that have gone extinct Others have undergone little change Indirect Evidence: Looking for patterns such as similarities and differences in species that are still alive a) Embryology b) Anatomy c) Vestigal structures d) Physiological evidence e) Biochemical evidence Embryology Study of organisms in the early stages of developement ex: what do the eggs look like? *see page 69 Anatomy Homologous structures Similar structure, different function Seal flippers and human arms have a different function but similar origin Analogous structures Similar function, different origin of structures Bat and insect wings perform the same function but have different origins Vestigal structures Structures or organs which no longer have a function (ex: human tailbone, male nipples) Physiological evidence Hormones which are the same between species Hormones such as progesterone and estrogen for human birth control pills come from horses Biochemical Evidence Similarities or differences between DNA Our DNA has some similarities to primates Patterns of evolution: Divergent evolution When one species can evolve to give rise to many different species Ex: One ancestor species diverges into two new species due to structural, behavioural or physiological changes to adapt to various environments Homologous structures provide evidence for divergence Patterns of evolution: convergent evolution When unrelated species develop similar characteristics because of adaptations to a similar environment and way of life Ex: tasmanian wolf (marsupial from australia) and Timber wolf (placental mammal from N.A.) Both are predators that look similar Analagous structures provide evidence for convergent evolution (*see pg 78, fig 2.19)
